System and method for scanning an intraoral cavity

ABSTRACT

According to the invention, a method and system are provided for scanning, and for facilitating scanning of, an intraoral cavity. The target parts of the intraoral cavity that it is desired to have scanned are identified, and the spatial s relationships between a scanning device and the target parts of the intraoral cavity suitable for enabling said target parts to be scanned by said scanning device, are also identified or otherwise determined. These relationships are then displayed, and the displayed relationships are used as a guide for scanning the intraoral cavity.

CROSS-REFERENCE

This application is a continuation application of U.S. application Ser.No. 12/980,587, filed Dec. 29, 2010, now U.S. Pat. No. 9,683,835, whichis a continuation of U.S. application Ser. No. 11/889,002, filed Aug. 8,2007, now U.S. Pat. No. 7,890,290, which is a continuation of U.S.application Ser. No. 11/365,589, filed Mar. 2, 2006, now U.S. Pat. No.7,286,954, which claims the benefit of U.S. Provisional Application No.60/657,705, filed Mar. 3, 2005, all of which are incorporated herein byreference in their entirety and to which applications we claim priorityunder 35 USC § 120.

FIELD OF THE INVENTION

This invention relates to a system and method for providing guidance forscanning the intra oral cavity to provide three dimensional data thatmay be subsequently used in prosthodontic and orthodontic procedures inthe intra oral cavity. In particular, the invention relates to suchsystems and methods that are computerized.

BACKGROUND OF THE INVENTION

In prosthodontic procedures designed to implant a dental prosthesis inthe intra oral cavity, the dental site at which the prosthesis is to beimplanted in many cases needs to be measured accurately and studiedcarefully, so that a prosthesis such as a crown or bridge, for example,can be properly designed and dimensioned to fit in place. A good fit isof the highest importance to enable mechanical stresses to be properlytransmitted between the prosthesis and the jaw, and to prevent infectionof the gums and so on via the interface between the prosthesis and thedental site, for example.

In the prior art, the dental site is prepared by the dentalpractitioner, and a positive physical model of the site is constructedusing known methods. Alternatively, the dental site may be scanned toprovide 3D data of the site. In either case, the virtual or real modelof the site is sent to the dental lab, which manufactures the prosthesisbased on the model. However, if the model is deficient or undefined incertain areas, or if the preparation was not optimally configured forreceiving the prosthesis, the dental technician has a more difficult jobahead than otherwise, and the design of the prosthesis may be less thanoptimal. For example, if the insertion path implied by the preparationfor a closely-fitting coping would result in the prosthesis collidingwith adjacent teeth, the coping geometry has to be altered to avoid thecollision, but this may result in the coping design being less optimal.Further, if the area of the preparation containing the finish line lacksdefinition, it may not be possible to properly determine the finish linean thus the lower edge of the coping may not be properly designed.Indeed, in some circumstances, the model is rejected and the dentalpractitioner must re-scan the dental site, or must rework thepreparation, so that a suitable prosthesis may be produced.

In orthodontic procedures it is also necessary to provide a model of oneor both jaws. Where such orthodontic procedures are designed virtually(herein also referred to as “numerically”), a virtual model of theintraoral cavity is also required, and this may be obtained, inter alia,by scanning the intraoral cavity directly, or by producing a physicalmodel of the dentition, and then scanning the model with a suitablescanner.

Thus, in both prosthodontic and orthodontic procedures, obtaining athree-dimensional (3D) model of a least a part of the intraoral cavityis an initial requirement. When the 3D model is a virtual model, themore complete and accurate the scans of the intraoral cavity are, thehigher the quality of the virtual model, and thus the greater theability to design an optimal prosthesis or orthodontic treatment.

Prior art methods of scanning the intraoral cavity do not provideguidance to the dental practitioner on how to ensure full and accuratescanning of parts of the cavity of interest for a particular orthodonticor prosthodontic procedure. Rather, the dental practitioner uses his orher judgment on site, and it is often the case that the scans of someareas of interest may be defective, while other unimportant areas may bescanned to great accuracy with details, which is wasteful of thepractitioner's and the patient's time.

SUMMARY OF THE INVENTION

Herein, “dental material” refers to any material associated with dentalstructures of the intra oral cavity, including but not limited tonatural dental materials such as for example enamel, dentine, pulp,dental roots, and non-natural dental materials such as for examplemetallic and non-metallic filings, restorations, crowns, bridges,copings, preparations, and so on.

Herein, “dental clinic” refers to the interface between a dentalpractitioner and a patent, and thus includes any physical entity, inparticular a clinic, in which there is interaction between a dentalpatient and a dental practitioner. While “dental practitioner” typicallyrefers to a dentist, doctor or dental technician, it also includesherein all other caregivers that may interact with a dental patientduring the course of a dental treatment. While “dental patient”typically refers to a person requiring the dental services of a dentalpractitioner, it also includes herein any person regarding whom it isdesired to create a 3D numerical model of the intra oral cavity thereof,for example for the purpose of practicing the same or for carrying outresearch.

The term “prosthesis” is herein taken to include any restoration and anyonlays, such as crowns and bridges, for example, and inlays, such ascaps, for example, and any other artificial partial or complete denture.

While the term “preparation” typically refers to the stump (includingthe finish line and optionally the shoulder) that is left of the tooththat is to be replaced by the prosthesis—typically a crown—and on whichthe crown is to be mounted, the term herein also includes artificialstumps, pivots, cores and posts, or other devices that may be implantedin the intraoral cavity in such a position or in a position that isoptimal for implanting the crown.

The term “prosthodontic procedure” refers, inter alia, to any procedureinvolving the intraoral cavity and directed to the design, manufactureor installation of a dental prosthesis at a dental site within theintraoral cavity, or a real or virtual model thereof, or directed to thedesign and preparation of the dental site to receive such a prosthesis.

The term “orthodontic procedure” refers, inter alia, to any procedureinvolving the intraoral cavity and directed to the design, manufactureor installation of orthodontic elements at a dental site within theintraoral cavity, or a real or virtual model thereof, or directed to thedesign and preparation of the dental site to receive such orthodonticelements.

The term “numerical entity” is used herein synonymously with virtualmodel, 3D model, and other such terms, and relates to a virtualrepresentation in a computer environment of a real object, typically adentition or at least a part of intraoral cavity, or of a real modelthereof, for example.

The term “scanning” and its analogues refer to any procedure directed atobtaining 3D topographic data of a surface, particularly of a dentalsurface, and thus includes mechanical methods, typically based on 3Dprobes for example, optical methods, including for example confocalmethods, for example as disclosed in WO 00/08415, the contents of whichare incorporated herein in their entirety by reference, or indeed anyother method.

The term “display” and its analogues refer to any means or method fordelivering a presentation, which may include any information, data,images, sounds, etc, and thus the delivery may be in visual and/or audioform.

The present invention is directed to a method for scanning an intraoralcavity, and thus to a corresponding method for facilitating scanning ofan intraoral cavity, the method comprising

(a) identifying target parts of the intraoral cavity that it is desiredto have scanned;

(b) identifying spatial relationships between a scanning device and saidtarget parts of the intraoral cavity suitable for enabling said targetparts to be scanned by said scanning device;

(c) displaying said relationships; and

(d) using said displayed relationships as a guide for scanning theintraoral cavity.

The method further comprises the step of scanning said intraoral cavityin a manner substantially conforming to said relationships.

The scanning substantially provides 3D data of said target parts for usein a predetermined procedure. Step (a) may include identifying ancillaryparts in said intraoral cavity associated with said target parts,wherein 3D data of said ancillary parts is also required for use in saidpredetermined dental procedure. Step (b) may comprise, for each saidtarget part and each said ancillary part, determining for said scanningdevice a series of spatial parameters, each comprising a scanningstation data sufficient for enabling said scanner to fully scan saidcorresponding target part or ancillary part. Optionally, the scanningstation data of said series include a proximity and a relativeorientation of said scanner with respect to said target part orancillary part such as to enable said scanner to obtain 3D topographicaldata of an area of said target part or ancillary part. The seriesprovide 3D topographical data for a corresponding plurality of saidareas, wherein said spatial parameters of said series are determinedsuch at least some adjacent said areas overlap one another.

In one embodiment, step (c) comprises displaying a nominal imagecomprising an image of at least a portion of an nominal intraoralcavity, comprising corresponding said target parts and said ancillaryparts, and an image of a nominal scanner in a spatial relationship withrespect to one another corresponding to the spatial relationship asdetermined in step (b) for at least one parameter of said series ofparameters. A series of said nominal images may be provided, each imagein said series corresponding to a different one of said parameters ofsaid series of parameters. The series of images can be displayed in anypredetermined sequence. Optionally, the nominal image comprises 3Dattributes. The image may comprise said nominal intraoral cavity at anydesired orientation with respect to a predetermined coordinate system.The coordinate system may comprise, for example, an orthogonal Cartesianaxes system. The orientation may optionally correspond to a real lifeview of the intraoral cavity of a patient from the vantage point of adental practitioner. Optionally, an audio and/or visual cue is providedfor prompting the user to proceed to the next image.

In another embodiment, step (c) comprises displaying indicia on aviewfinder capable of providing a video image of the field of view ofsaid scanner, said indicia being indicative of a desired position forassociating a predetermined portion of said target parts or ancillaryparts in a particular manner with respect therewith. The indicia maycomprise, for example, an “+” or an “X” or any other suitable symbol,which may be, for example, geometrical, alphanumeric and so on.

In a variation of this embodiment, the indicia comprise a symbolrepresentative of a profile corresponding to an expected view of saidtarget part or ancillary part in said viewfinder. Optical or imagerecognition methods can be applied to said video image for providing aprofile of the image, said symbol comprising said profile. For example,the profile comprises a shaped line shaped as an outline of a tooth asseen via said viewfinder. The symbol may comprise a shaped line shapedas an outline of a tooth seen in any one of top view, buccal view orlingual view, for example.

Optionally, a series of indicia are provided, each indicia in saidseries corresponding to a different one of said parameters of saidseries of parameters. Said series of indicia may be displayed in apredetermined sequence, a next indicia being displayed after theintraoral cavity has been scanned according to the previous saidparameter and corresponding indicia. Said next indicia may be displayedtogether with the immediately preceding indicia. Optionally, indiciarelating to different said parameters may be displayed in differentcolors one from another.

The aforesaid procedure may be, for example, a prosthodontic procedurefor a crown with respect to a preparation, said target parts comprisingsaid preparation, and said ancillary parts comprising at least a portionof the teeth adjacent to said preparation and facing said preparationfrom the opposed jaw.

The aforesaid procedure may be, for example, a procedure is aprosthodontic procedure for a bridge with respect to a plurality ofpreparations, said target parts comprising said preparations, and saidancillary parts comprising at least a portion of the teeth adjacent to afurthermost distal preparation and adjacent a furthermost mesialpreparation, and at least a portion of the teeth facing saidpreparations from the opposed jaw.

The aforesaid procedure may be, for example, a procedure is anorthodontic procedure, and said target parts comprise the full dentitionof at least one jaw of said intraoral cavity. Typically the method ofthe invention is a computerized method, i.e., executed partly or fullywith the aid of a processing unit such as a computer. Nevertheless, atleast some embodiments may be executed without the need of a computer.

The present invention also relates to a computer readable medium thatembodies in a tangible manner a program executable for guiding thescanning of the intraoral cavity of a patient, comprising:

(a) a first set of data representative of target parts of the intraoralcavity that it is desired to have scanned;

(b) a second set of data representative of spatial relationships betweena scanning device arid said target parts of the intraoral cavitysuitable for enabling said target parts to be scanned by said scanningdevice.

The computer readable medium may further comprise means such asmanipulation routines, computer instructions, and so on, for example,for manipulating said second set of data for enabling displaying saidsecond data.

The medium may comprise any one of optical discs, magnetic discs,magnetic tapes, and so on, for example.

The present invention is also directed to a system for guiding thescanning of an intraoral cavity, comprising:

(A) input module for identifying target parts of the intraoral cavitythat it is desired to have scanned;

(B) processing module for generating spatial relationships between ascanning device and said target parts of the intraoral cavity suitablefor enabling said target parts to be scanned by said scanning device;

(C) display module for displaying said relationships.

The system preferably also comprises a suitable scanner for scanningaccording to said relationships

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, a number of embodiments will now be described, by wayof non-limiting example only, with reference to the accompanyingdrawings, in which:

FIG. 1 shows a block diagram of a scanning process according to anembodiment of the invention.

FIG. 2 shows a block diagram of a scanning system according to anembodiment of the invention.

FIG. 3 shows a virtual representation of a dentition enabling targetareas to be chosen interactively.

FIG. 4 illustrates target parts and ancillary parts of an intraoralcavity associated with a crown prosthodontic procedure.

FIG. 5 shows a buccal view of an idealised virtual model of a nominalintraoral cavity showing a plurality of scanning stations.

FIG. 6 shows a top view of an idealised virtual model of a nominalintraoral cavity showing a plurality of scanning stations.

FIG. 7 shows the relationship between an scanning station and a dentalsurface being scanned thereat.

FIGS. 8a and 8b illustrate examples of display output using the systemof FIG. 2 according to one embodiment.

FIGS. 9a and 9b illustrate examples of display output using the systemof FIG. 2 according to another embodiment.

FIGS. 10a , 10 b, 10 c illustrate the embodiment of FIGS. 9a, 9b , usedfor guiding scanning from one scanning station to a next scanningstation.

FIGS. 11a and 11b illustrate examples of display output according to avariation of the embodiment of FIGS. 9a , 9 b.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a block diagram of the 3D data acquisition process100 according to an embodiment of the invention, and FIG. 2 illustratesthe main elements of a system 200 for carrying out the method accordingto an embodiment of the invention. The system 200 typically comprises amicroprocessor or any other suitable computer, having an input interfaceor module 210 such as a keyboard, mouse, tablet, and so on, an outputdevice or display means or module 220, typically a screen or monitor butmay additionally or alternatively include a printer, or any otherdisplay system, a processing unit or module 230 such as for example aCPU, and a memory 240. In some embodiments, a suitable scanner 250 forobtaining 3D data of the intraoral cavity is also operatively connectedto the system 200 and interacts therewith, while in other embodimentsthe scanner 250 may provide the 3D data to another system notnecessarily connected in any way with system 200. Advantageously, aprobe for determining three dimensional structure by confocal focusingof an array of light beams may be used, for example as manufacturedunder the name of CB-CAD or as disclosed in WO 00/08415, the contents ofwhich are incorporated herein in their entirety. Alternatively, scanningof the dental cavity to provide the 3D data may be accomplished usingany suitable apparatus typically comprising a hand held probe.

At step 110, the target parts of the intraoral cavity are identified.The target parts are the parts (also referred to herein as zones orareas) of the intraoral cavity which form the focus of a particulardental procedure for a particular patient and regarding which it isdesired to obtain the 3D topographical or surface data thereof. Thetarget parts typically include the part of the tooth or the teeth, orother dental material on which the particular procedure is to beperformed, and in some cases may include the full mandibular ormaxillary arches, or both arches. For example, the procedure may be aprosthodontic procedure involving a crown prosthesis to be designed andfabricated for fitting onto a preparation at a particular dental site.In such a case, the dental practitioner inputs into processing unit 230the tooth which has been targeted for the procedure, identifiedaccording to any suitable convention. For example, and referring to FIG.3, the display 220 may be used to display a standard image or graphicalrepresentation 211 of a nominal intraoral cavity, either with threedimensional (3D) attributes or a simple two dimensional (2D)representation. Alternatively, though, a non-graphical (for examplealphanumeric) representation of the intraoral cavity may be provided.Thus, and referring to the example illustrated in FIG. 3, therepresentation 211 includes a plurality of icons or images or symbols212, one each corresponding to the teeth in a normal adult or child (theage of the patient having first been input to the processing unit 230).The tooth which is to be the target of the procedure may be identifiedby “clicking” with the aid of a mouse, for example, on the appropriatesymbol 212. Alternatively, any other interactive method may be used forchoosing the target tooth, for example by means of a touch screenarrangement. In another example, the identity of the target tooth may bemanually input to the processing unit 230 using any conventionalnomenclature, a unique coding convention, by selection on a drop-downmenu or the like, or in any other suitable manner, the processing unit230 having been suitably programmed to recognise the choice made by theuser.

Alternatively, for a prosthodontics procedure involving a bridge, thetwo or more teeth that are to be worked on to provide preparations toreceive the bridge are identified, for example in a similar to thatdescribed above, mutatis mutandis. For orthodontic procedures typicallyall of the teeth in one or both jaws are required. In such a case, allof the teeth of the upper jaw, lower jaw or both jaws may be chosen bymeans on a single appropriate symbol, for example as indicated at 213,214, 215, respectively, in FIG. 3.

The manner in which the intraoral cavity needs to be scanned may dependon the procedure to be applied thereto, as will become clearer as thedescriptions proceeds. Thus, the dental practitioner also inputs to theprocessing unit 230 the identity of the actual procedure. For thispurpose, the dental practitioner may choose the procedure from a numberof preset options on a drop-down menu or the like, from icons or via anyother suitable graphical input interface. Alternatively, the identity ofthe procedure may be input in any other suitable way, for example bymeans of preset code, notation or any other suitable manner, theprocessing unit 230 having been suitably programmed to recognise thechoice made by the user. By way of non-limiting example, the proceduresmay be broadly divided into prosthodontic and orthodontic procedures,and then further subdivided into specific forms of these procedures, asknown in the art.

The type of scanner 250 to be used is also input to the processing unit,typically by choosing one among a plurality of options. If the scannerthat is being used is not recognisable by the processing unit 230, itmay nevertheless be possible to input operating parameters of thescanner thereto instead. For example, the optimal spacing between thescanner head and the tooth surface can be provided, as well as thecapture area (and shape thereof) of the dental surface capable of beingscanned at this distance. Alternatively, other suitable scanningparameters may be provided. In any case, it may be desired that thevirtual model of the dentition, provided using the scanners, may bedimensionally related to the real dentition in a known manner, so thatdimensional measurements of the virtual model may be made.

In the next step 120, the processing unit 230 identifies the requiredspatial relationships that are required for scanning the appropriateparts of the intraoral cavity so that complete and accurate 3D data maybe obtained for the procedure in question. This step utilises the dataalready provided in step 110 for 30 establishing the optimal manner forscanning the intraoral cavity, and thus will depend on the nature of theaforesaid data. Further, according to the method of the invention,additional or ancillary parts of the intraoral cavity that need to bescanned for the particular procedure are also identified, and thespatial relationship between the scanner and these parts are identifiedor determined. Having identified the target parts and ancillary parts, ascanning protocol is identified or determined by relating the type ofscanner, resolution thereof, capture area at an optimal spacing betweenthe scanner head and the dental surface to the target parts and theancillary parts, either separately or together. The scanning protocoltypically comprises a series of scanning stations spatially associatedwith the dental surfaces of the target part and the ancillary part.Preferably, significant overlapping of the images or scans capable ofbeing obtained at adjacent scanning stations is designed into thescanning protocol to enable good registration, and the 3D data obtainedat each scanning station is stitched together to provide a composite 3Dvirtual model, as is known in the art. A number of examples will now bedescribed.

FIG. 4 illustrates an idealised portion 300 of the intraoral cavity of apatient requiring a crown prosthesis on a preparation P having teeth A,B, adjacent thereto, and teeth A′, P′ and B′ in opposed relationshipthereto from the other jaw. This idealised portion 300 is typically a 3Dvirtual model of an idealised full dentition of an adult that is storedin the memory 240 of the system 200. By idealised is simply meant thatthe idealised dentition comprises 3D models of all of the teeth of anadult in their normal relative positions, the 3D models typically beingstandardised according to the statistical norm regarding size, shape andso on as commonly found in the population. Of course, for the purpose ofthe invention, any 3D virtual model may be suitable, so long as itincludes the 3D virtual models of the teeth corresponding to the teethof the patient in the required target part and ancillary part. Thememory 240 may also comprise idealised virtual models of the teeth ofchildren or of special population groups, and thus the user typicallyspecifies (and may optionally be prompted to 30 do so by the system 200)the age of the patient, or other attribute that best decides the closestidealised virtual model with respect thereto. The memory 240 alsocomprises, for each virtual tooth model of the 3D virtual model 300, anidealized virtual preparation model, and according to the prosthodonticsprocedure required by the patient, one or more of the virtual teeth maybe replaced with the corresponding one or more virtual preparations.

The target area or part to be scanned is represented by the dotted lineT, and includes the preparation P, including the finish line LT, andpart of the original tooth above the gumline. When the target area isscanned very accurately, it is possible for the internal surface of acorresponding coping or prosthesis to be accurately designed. Ancillaryparts of the intraoral cavity are included in dotted line AT, andcomprise parts of the adjacent and opposed teeth, principally teeth A,B, P′, and often to a lesser extent teeth A′ and B′ or parts thereof.Typically, but not necessarily, the resolution of the scanned data forthe ancillary parts AT may be less than for the target part T, since themanufacturing accuracy for the external surfaces of the crown prosthesis(the design of which is dependent on the dental surfaces of theancillary parts) may be substantially less than for the internal surfaceof the coping or prosthesis. According to the specific nature orproperties of the scanner, including the resolution thereof, capturearea at an optimal spacing between the scanner head and the dentalsurface to the target parts and the ancillary parts, the scanningprotocol may be designed as follows.

Referring to FIG. 7, for example, at each scanning station S_(i) (alsoreferred to herein as an image capture station), 3D data within an areaI_(i)′ of the dental surface X of a tooth or preparation, for example,may be captured by the scanner 250, and this area may be represented atthe scanning station S_(i) by a projection I_(i) of area I_(i)′ on aplane orthogonal to the scanning axis OA of the scanner, and displacedfrom the dental surface by a dimension t. This dimension t is typicallythe optimal spacing of the particular scanner with respect to the dentalsurface X for providing a scan area equivalent to I_(i) but may be anyother suitable spacing. The shape of the area I_(i) will generallydepend on the scanner, and is herein represented by a rectangle. Theorientation of the scanning axis OA can be related to a referencecoordinate system, for example orthogonal Cartesian axes 320 definedwith respect to the model 300, and which are typically easily identifiedin the real intraoral cavity. Referring to FIGS. 5 and 6, the processingunit 230 determines a plurality of scanning stations S_(i) surroundingthe target part T and the ancillary part AT (referring also to FIG. 4)such that the corresponding areas I_(i)′, in which 3D data is obtained,together cover the full extent of the dental surfaces of interesttherein (wherein i=1, 2, 3, . . . 10, 11, 12, 13, 14 . . . ). Forexample, in FIG. 5, areas I₁ , I₂, I₃ and areas I₄, I₅, I₆ represent twosets of three overlapping zones each at approximately two differentheights with respect to the gum G which may be sufficient to define abuccal portion of the target part T and the ancillary part AT of thelower jaw of FIG. 4. Similar areas may be required form the lingualside. In FIG. 6, areas I₄, I₅, 1 ₆ are represented by U-shaped symbols,wherein the arms of the U represent the direction along which the scanis taken, i.e., the spatial position of the scanning axis OA of thescanner, and the middle portion of the U represents the correspondingprojection I_(i) as seen edge-on. Thus, exemplary additional areas I₁₀and I₁₁ represent additional scanning stations not I₇, I₈, I₉, I₁₂, I₁₃,I₁₄, in FIGS. 5 and I_(ii) represent additional scanning stations notcoplanar with the scans at areas I₄, I₅, I₆. Similarly, the areas I₇,I₈, I₉, I₁₂, I₁₃, I₁₄, in FIGS. 5 and 6 represent additional scanningareas taken from above the tooth, with greater overlap between areasbeing provided in the vicinity of the target part T. For example, areasI₁₃, I₁₄, being more face-on with respect to parts of the finish linemay provide greater accuracy thereof. The location and orientation ofscanning stations S_(i) are determined such that the areas I_(i)′ of theidealised model corresponding to these stations adequately cover thecorresponding target parts T and ancillary parts AT thereof. Thus, byreproducing these locations and orientations of the scanner 250 withrespect to the real intraoral cavity, the required 3D data of the targetpart T and ancillary part AT may be obtained, as will be described ingreater detail hereinbelow.

The scanning protocol for the dental surfaces of the opposed jaw thatare included in the target part T and the ancillary part AT may beobtained in a similar manner to that described above for the lower jaw,mutatis mutandis.

Typically, the scanning protocol will differ when different scanners areused for the same target area, depending on the capture characteristicsof the scanner used. Thus, a scanner capable of scanning a larger dentalarea with each scan (e.g., having a larger field of view) will requireless scanning stations to be defined in the scanning protocol than ascanner that is only capable of capturing 3D data of a relativelysmaller dental surface. Similarly, the number and disposition ofscanning stations for a scanner having a rectangular scanning grid (andthus providing projected scanning areas I_(i) in the form ofcorresponding rectangles) will typically be different from those for ascanner having a circular or triangular scanning grid (which wouldprovide projected scanning areas I_(i) in the form of correspondingcircles or triangles, respectively).

In another example (not illustrated) relating to a prosthodonticsprocedure for a bridge having a single or a plurality of poetics, thereare generally two target parts, relating to one or the other of the twopreparations on which the bridge is to be anchored, and the ancillaryparts to be scanned include at least part of the teeth adjacent to thefurthermost distal preparation and adjacent the furthermost mesialpreparation, and at least a portion of the teeth facing the preparationsfrom the opposed jaw.

In another example (not illustrated) relating to a prosthodonticsprocedure requiring a restoration on the buccal or lingual part of aparticular tooth, only this target part may need to be scanned in thepatient together with the occlusal surfaces of the some of the teeth ofthe opposite jaw as ancillary parts.

In yet another example (not illustrated) relating to an orthodonticprocedure for one or both jaws, the target part may comprise the fulldentition of one or both jaws, respectively.

According to the invention, the system 200 may calculate each time a 30new idealised scanning protocol based on the parameters of the scanner,the procedure, the dental site of the procedure, age of the patent, andso on, and as applied to the idealised virtual model 300.

Alternatively, all the necessary scanning protocols are previouslycalculated for every type of scanner, procedure, age group and so on,and stored in memory 240, the most suitable protocol being retrievedtherefrom when identified according to the particularpatient/procedure/scanner parameters that are provided. In this case,the virtual model 300 may not be needed for the purpose of determiningcustomised scanning protocols. Thus, it is possible to provide all thenecessary guidance for a particular procedure in printed form, a printedbook or pamphlet, for example, by means of a movie or video clip, or inany other communication medium, wherein the user would search for theappropriate guidance images or the like according to the particularparameters of the patient in question, via an index or the like forexample, and then open the book/movie and so on at the relevantpages/scene etc., to obtain the guidance required.

Alternatively, the memory 240 comprises a standard scanning protocol foreach different type of procedure, and this protocol is modified by theprocessing unit 230 to take account of at least one of the parametersincluding: age of dental patient, dental target part, scannercharacteristics, and so on.

In step 130, the spatial relationship between the scanning stationsS_(i) and the intraoral cavity are displayed, so that in step 140 thesedisplayed relationships may be used as a guide by the dentalpractitioner for scanning the intraoral cavity in a manner suitable forobtaining 3D data appropriate for the particular procedure beingconsidered There are many ways of displaying the aforesaid spatialrelationships, sonic examples of which will now be described.

Referring to FIGS. 8a and 8b , for example, a pair of perspective viewimages K_(i) may be displayed, on a screen 220 or as printed material,for example, corresponding to the spatial relationship of the scanner250 with respect to the idealised intraoral cavity 300 at a particularscanning station S_(i). Additionally or alternatively, a plurality ofimages showing the relationship at any other desired vantage point(viewpoint) may be provided, including for example the vantage point aswould be seen by a dental practitioner with respect to a real intraoralcavity, either by default or by being chosen by the user by interactingwith processing unit 230. Optionally, a dynamic image may be provided,in which the user can change the vantage point of the imageinteractively, in a manner known in the art. Alternatively, a video clipor the like may be provided for providing the user with a sequence ofoperations of the scanner etc.

Images K_(i) may be composites of virtual models of the scanner 250 andof the intraoral cavity 300 (typically the aforesaid idealised virtualmodel) stored in memory 240. These virtual models are manipulated by theprocessing unit 230 to provide the correct spatial relationship, invirtual space, according to the particular scanning station S_(i)previously determined, and can be displayed as two dimensional images ina manner known in the art. Optionally, the position of the scanningstation S_(i) and the direction of the scanning axis OA can be displayedwith respect to the intraoral cavity 300, additionally or alternativelyto the scanner. The scanning axis OA is typically defined as orthogonalto the scanning face 255 of the scanner, but may be defined according toany other preknown suitable geometric or other parameter of the scanner.The images K_(i) can optionally comprise a representation of thecoordinate system, for example orthogonal axes 320, in the orientationappropriate to the vantage point being viewed.

For the purpose of images K_(i), it may be possible to display the imageof the dental surfaces as having 3D attributes and realistic dentalmorphologies, for example as illustrated in FIGS. 8a and 8b , oralternatively, each dental surface may be represented, for example, by ageometrical form—for example simple wedges representing incisors, conesrepresenting canines, and cylinders representing molars. Optionally, asummary composite image may be first provided (not shown) illustratingthe full protocol, for example as a plurality of symbols (e.g. indiciasuch as “X” or “+”, or frames representing the projected areas I_(i),and so on) may be superposed over one or more images of the idealiseddentition—for example, in a manner similar to that illustrated in FIGS.5 and 6.

Further optionally, the idealised virtual model appearing in imagesK_(i) may be custom-modified to show a virtual preparation at eachcorresponding dental site where a real preparation is to be found, andalso virtual teeth may be removed from the model where none are to befound in the real intraoral cavity—for example where teeth have beenremoved for accommodating a pontic. These features can furtherfacilitate identification of the positions and orientations of thescanner at each of the scanning stations S_(i).

Further optionally, non-image data may be provided identifying theposition and orientation of the scanner at each scanning station S_(i),and this data may be provided, for example, in the form of a tablelisting suitable corresponding geometric data, and also including, forexample the spacing between the scanner scanning face 255 and the dentalsurface of interest, an identification of the particular surface beingscanned, and so on. Alternatively, the relationships in step 130 may bedisplayed in alphanumeric form, as a set of instructions or statementsdescribing the relative positions of the scanner and teeth, for example.Alternatively, the relationships in step 130 may be displayed in audibleform, wherein for example such instructions or statements are broadcastby a speaker or the like, either from a prerecording, or syntheticallycreated by the system 200.

Further optionally, the scanning stations S_(i) may be successivelydisplayed in any desired order, for example in an order such as tominimise displacement of the scanner between each successive scan. Inthis embodiment of step 130 is followed by the step 140 of using thedisplayed relationships as a scanning guide, and step 150 of scanningthe intraoral cavity in a manner substantially conforming to saidrelationships. To facilitate the dental practitioner's work, the imagescorresponding to a next scanning station are, optionally, not displayeduntil the practitioner is confident that he/she has properly scanned theintraoral cavity as required by the current scanning station. This maybe accomplished by operatively connecting the scanner 250 to theprocessing unit 230, and prompting the user whether to display the nextscanning station every time a scan is taken (and which is detected bythe unit 230). Alternatively, it may be possible, after each scan, todisplay a video image as taken by the scanner with an idealised 2Dvirtual image of the idealised virtual model as seen from the vantagepoint of the scanner for this scanning station, and the user can comparethe two images and decide whether or not the particular scan is likelyto have sufficiently conformed with the desired relationship.

A second embodiment of step 130 is illustrated in FIGS. 9a and 9b , andin this embodiment, use is made of the video image capturingcapabilities of the scanner 250, which is configured with suchcapabilities, for guiding the same. A suitable symbol, such ascross-hairs 400, occlusal line 410, and so on may be superimposed on theviewfinder of the scanner 250, typically displayed on the screen 220 (orprinted for example). In this embodiment, the spatial relationships ofstep 120 are displayed from the vantage point of the scanner 250, andtakes the form of providing a reference marker, such as the aforesaidcross-hairs 400, for example, on the screen where a particular part ofthe dental surface (e.g., the centre of a tooth viewed in the particulardirection of the scanning axis) being viewed should be centred. Forexample, in FIG. 9a , the appropriate scan for the scanning station maybe taken when the upper tooth 405 and the lower tooth 406 (previouslyidentified by the system as being the subject of the scan) as imagedfrom a buccal direction by the scanner are each centralised with respectto the upper and lower cross-hairs 400. Similarly, in FIG. 9b , thetooth 407 being imaged from above is centralised with respect tocross-hairs 400. The cross-hairs may further comprise a ring 401 whichfurther facilitates centering the tooth 407 as viewed via the scanner250 with respect to the cross-hairs 400.

Proceeding to and identifying the next scanning station is facilitatedby displacing the cross-hairs 400 to a position on the screen where thelast position of the cross-hairs 400 appears in the next (now current)position of the scanning station. This is accomplished automatically bythe processing unit 230 when the user is satisfied that the previousscan was properly taken, for example as described earlier in connectionwith the embodiment of FIGS. 8a, 8b , mutatis mutandis. The scanner isthen moved so that the cross-hairs 400 (still associated in virtualspace with the previous scanning station, and now appearing at therelocated position on the viewfinder) is again centralised with theprevious dental surface, which has been effectively displaced from thecentral position of the screen to a position once again associated withthe now-displaced cross-hairs 400. This automatically aligns the scannerwith the next scanning station. For example, referring to FIGS. 10a to10c , FIG. 10a illustrates an image L in buccal view of a series ofteeth, with the cross-hairs 400 centralised over one particular tooth410, the adjacent teeth 411 and 412 being partially visible. When theuser is satisfied that a suitable scan was taken at this scanningstation, this is made known to the system 200 in any suitable manner,and the cross-hairs 400 is moved from the previous position at thecentre of the screen to the right, such that only the left hand portion401 of the cross-hairs 400 is now visible. The user then moves thescanner such as to renew the relative position of tooth 410 with respectto cross-hairs 400 in the viewfinder, to for example as illustrated inthe image of FIG. 10b , which now brings the next dental surface to bescanned, in this case tooth 411, into the main part of the viewfinder toprovide image L′. The relative position of the elements in the previousimage L is shown as a dotted box. When this is accomplished to thesatisfaction of the user, the old position of the cross-hairs 400 isremoved from the screen, and repositioned at the centre of the screen,as shown at the dotted lines 400′. A scan can now be performed at thisposition, which corresponds to a scanning station. To move to the nextscanning station illustrated in FIG. 10 c, the new position of thecross-hairs 400 is relocated, for example to the lower part of theviewfinder, and the user correspondingly translates the scanner so as tore-locate tooth 411 to maintain the previous relative position withrespect to the cross-hairs 400, providing image L″, and the position ofthe previous image L′ is shown in the dotted box in this figure. Thisprocess is repeated until all the scanning stations have been passed. Itmay be necessary to change to direction of the scanning entirely, forexample from buccal (FIG. 9a ) to upper (FIG. 9b ), and this can be doneby guiding the user to a particular tooth where the transition isrequired, and then for example changing the form of the referencemarker—for example, from the “+” indicia to one also including a circle409 (e.g. as illustrated in FIG. 9b )—signifying that an upper viewshould now be taken of the current tooth (or preparation or whateverdental surface is being considered). Additionally or alternatively,written, or graphic prompts may be provided in the screen, or vocal orother audio prompts provide via a speaker (not shown) urging the user tochange position, and/or to move to a different dental site, specifiedaccording to the next scanning station.

In a variation of the second embodiment of steps 130 and 140 describedabove, optical recognition (also known as image recognition) methods maybe employed for identifying features of the dental surface being scannedat the current scanning station for guiding the user to the nextscanning station. For example, and referring to FIGS. 11a and 11 b,image M is a video image corresponding to the latest scan, obtained atthe current scanning station. Image M shows the relative positions ofvarious dental surfaces such as a tooth 430 in lingual view, flanked byadjacent teeth 431, 432. Suitable optical or image recognition means areapplied to image M, which is first isolated in processing unit 230 bymeans of a suitable frame grabber, and a profile of interest, MP, isdetermined. Such a profile MP typically comprises an external edge ofone or more of teeth 430, 431, 432 as seen from the vantage point ofscanner 250, and thus typically comprises a fictitious line separatingtwo zones that are optically different—the teeth and the background, forexample. The profile MP is then reproduced as an image in the viewfinderin its original relative position in image M. Then the processing unit230 calculates the movement of the scanner required to move to the nextscanning station, and applies this movement, in a virtual manner to theprofile MP, repositioning the profile MP to position MP′, or at last apart thereof, in the viewfinder, as illustrated in FIG. 11 b. (This ishow the new position of cross-hairs 400 described above may in practicebe calculated as well, for example.) The user then moves the scanner250, mimicking the virtual movement previously calculated, until theimage seen by the viewfinder is brought into alignment with therepositioned profile MP′. FIG. 11b shows image M′ obtained prior to fullalignment—the scanner 250 having to be moved in the direction of arrow450 until the profile MP′ is superposed on part of the edges MP″ of theteeth as seen via the viewfinder.

The guiding of the dental practitioner between the different scanningstations has been described above in graphical terms. Optionally oralternatively, the guiding may take any suitable form. For example, oralcommands may be provided, asking the practitioner to now move thescanner to the left 3 mm and upwards 2 mm, for example, using anysuitable speech software operating on scanning station data inputsprovided by the processing unit 230. Alternatively, non-oral audiocommands may be provided, for example coded bells or beeps, the patternand intensity thereof being capable of being interpreted by the user interms of the required movement in a number of directions, for example.

Additionally or alternatively, non-graphical means may be used forguiding the user between scanning stations. For example, suitable LED'smay be provided in the viewfinder, or images of arrows, for example, forguiding the user in the required directions to the next scanningstation.

Advantageously, the scanner 250 comprises an inertial system or asuitable tracking system, that is capable of determining a change ofposition and/or orientation thereof relative to a datumposition/orientation. Thus, the actual position/orientation of thescanner 250 can be checked automatically against the desired positionfor the next scan, and any suitable means—audio and/or visual forexample—may be used for guiding the user to the correct position basedon the difference between the current position and the desired position.For example, a beep may be sounded the frequency of which increases thecloser the scanner 250 is to the desired position. Optionally, a secondinertial or tracking system may be coupled to the head or jaws of thepatient, so that any movement thereof may be compensated for.

Optionally, a series of indicia may be provided, each indicia in theseries corresponding to a different scanning station. The series ofindicia may be displayed m a predetermined sequence, a next indiciabeing displayed after the intraoral cavity has been scanned at theprevious scanning station with its corresponding indicia. Optionally,the next indicia may be displayed together with the current, i.e., theimmediately preceding indicia. The indicia relating to different saidparameters are displayed in different colors one from another. Thus,these indicia help to identify which scanning station the user is at,and which is the next station, for example. The indicia may comprise aseries of numbers (for example “1/4”, “2/4”, “3/4”, “4/4”) or symbols,for example.

In another aspect of the present invention, a computer readable mediumis provided that embodies in a tangible manner a program executable forguiding the scanning of the intraoral cavity of a patient. The computerreadable medium comprises:

(a) a first set of data representative of target parts of the intraoralcavity that it is desired to have scanned;

(b) a second set of data representative of spatial relationships betweena scanning device and said target parts of the intraoral cavity suitablefor enabling said target parts to be scanned by said scanning device;

(c) means for displaying said second data.

The medium may comprise, for example, optical discs, magnetic discs,magnetic tapes, and so on.

According to some aspects of the invention, a method and system areprovided for scanning, and for facilitating scanning of, an intraoralcavity. The target parts of the intraoral cavity that it is desired tohave scanned are identified, and the spatial relationships between ascanning device and the target parts of the intraoral cavity suitablefor enabling said target parts to be scanned by said scanning device,are also identified or otherwise determined. These relationships arethen displayed, and the displayed relationships are used as a guide forscanning the intraoral cavity.

In the method claims that follow, alphanumeric characters and Romannumerals used to designate claim steps are provided for convenience onlyand do not imply any particular order of performing the steps.

Finally, It should be noted that the word “comprising” as usedthroughout the appended claims is to be interpreted to mean “includingbut not limited to”.

While there has been shown and disclosed exemplary embodiments inaccordance with the invention, it will be appreciated that many changesmay be made therein without departing from the spirit of the invention.

What is claimed is:
 1. A method for providing scanning guidance for ascanning device, comprising: (a) receiving, at a computer system, userinput selecting target parts of an intraoral cavity to be subsequentlyscanned by said scanning device; (b) determining, using the computersystem, spatial relationships between the scanning device and saidtarget parts of the intraoral cavity suitable for enabling said targetparts to be subsequently scanned by said scanning device, wherein visualguide instructions for positioning and orienting said scanning deviceare generated by the computer system based on said spatialrelationships; and (c) displaying, with the computer system on adisplay, said visual guide instructions for positioning and orientingsaid scanning device relative to the intraoral cavity in a mannersubstantially conforming to said spatial relationships; wherein saidvisual guide instructions comprise a symbol representative of a profilecorresponding to an expected view of said target parts or of ancillaryparts in said intraoral cavity associated with said target parts, theexpected view corresponding to the determined spatial relationships, andthe symbol comprising a line defining an interface between a pluralityof image zones.
 2. The method according to claim 1, wherein saidscanning device provides 3D data of said target parts for use in apredetermined dental procedure.
 3. The method according to claim 2,wherein said step (a) includes receiving user input identifying saidancillary parts in said intraoral cavity associated with said targetparts, wherein 3D data of said ancillary parts is also provided for usein said predetermined dental procedure; said step (b) comprises, foreach said target part and each said ancillary part, determining for saidscanning device a series of spatial parameters, each comprising scanningstation data for enabling said scanning device to fully scan saidcorresponding target part or ancillary part; wherein said scanningstation data of said series of spatial parameters includes a proximityand a relative orientation of said scanning device with respect to saidtarget part or ancillary part such as to enable said scanning device toobtain 3D topographical data of an area of said target part or ancillarypart; wherein said series provides 3D topographical data for acorresponding plurality of said areas, wherein said spatial parametersof said series are determined such that at least some adjacent saidareas overlap one another.
 4. The method according to claim 3, whereinstep (c) comprises displaying a nominal image comprising an image of atleast a portion of a nominal intraoral cavity comprising correspondingsaid target parts and said ancillary parts, and an image of a nominalscanning device, wherein the nominal intraoral cavity and the image ofthe nominal scanning device are displayed in a spatial relationship withrespect to one another corresponding to the spatial relationship asdetermined in step (b) for at least one spatial parameter of said seriesof spatial parameters.
 5. The method according to claim 4, wherein aseries of said nominal images are provided, each image in said seriescorresponding to a different one of said spatial parameters of saidseries of spatial parameters.
 6. The method according to claim 5,wherein said series of nominal images is displayed in a predeterminedsequence.
 7. The method according to claim 4, wherein said nominal imagecomprises 3D attributes, and wherein said nominal image comprises saidnominal intraoral cavity at any desired orientation with respect to apredetermined coordinate system.
 8. The method according to claim 7,wherein said orientation corresponds to a real life view of theintraoral cavity of a patient from the vantage point of a dentalpractitioner.
 9. The method according to claim 3, wherein step (c)comprises displaying indicia on a viewfinder capable of providing avideo image of a field of view of said scanning device, said indiciabeing indicative of a desired position for associating a predeterminedportion of said target parts or ancillary parts in a particular mannerwith respect therewith.
 10. The method according to claim 9, whereinsaid expected view comprises a view from said viewfinder.
 11. The methodaccording to claim 10, wherein optical recognition methods are appliedto said video image for providing a profile of the image, said symbolcomprising said profile.
 12. The method according to claim 11, whereinsaid profile comprises a shaped line shaped as an outline of a tooth asseen by said viewfinder.
 13. The method according to claim 10, whereinsaid symbol comprises a shaped line shaped as an outline of a tooth seenin any one of a top view, buccal view or lingual view.
 14. The methodaccording to claim 3, wherein said procedure comprises a prosthodonticprocedure for a crown with respect to a preparation, said target partscomprising said preparation, and said ancillary parts comprising atleast a portion of the teeth adjacent to said preparation and facingsaid preparation from the opposed jaw.
 15. The method according to claim3, wherein said procedure comprises a prosthodontic procedure for abridge with respect to a plurality of preparations, said target partscomprising said plurality of preparations, and said ancillary partscomprising at least a portion of the teeth adjacent to a furthermostdistal preparation and adjacent a furthermost mesial preparation, and atleast a portion of the teeth facing said plurality of preparations fromthe opposed jaw.
 16. The method according to claim 2, wherein saidprocedure comprises an orthodontic procedure, and said target partscomprise the full dentition of at least one jaw of said intraoralcavity.
 17. A system for scanning of an intraoral cavity, the systemcomprising: a scanning device; an input module configured to receive auser input selecting target parts of the intraoral cavity to besubsequently scanned by said scanning device; a processing moduleconfigured to determine spatial relationships between the scanningdevice and said target parts of the intraoral cavity suitable forenabling said target parts to be subsequently scanned by said scanningdevice and to generate, based on said spatial relationships, visualguide instructions for positioning and orienting said scanning devicerelative to the intraoral cavity in a manner substantially conforming tosaid spatial relationships; and a display module comprising a displayconfigured to display said spatial relationships so as to provide avisual guide protocol for a user to position and orient said scanningdevice relative to the intraoral cavity in a manner substantiallyconforming to said spatial relationships during scanning of saidintraoral cavity, thereby providing guidance for subsequent scanning ofsaid target parts by said scanning device; and wherein said visual guideinstructions comprise a symbol representative of a profile correspondingto an expected view of said target parts or of ancillary parts in saidintraoral cavity associated with said target parts, the expected viewcorresponding to the determined spatial relationships, and the symbolcomprising a line defining an interface between a plurality of imagezones.
 18. The system according to claim 17, wherein said scanningdevice is configured for scanning according to said spatialrelationships.
 19. The system according to claim 18, wherein saidscanning device comprises a probe for scanning according to said spatialrelationships.
 20. The system according to claim 17, wherein saidscanning device is configured to provide 3D data of said target partsfor use in a predetermined dental procedure.